This invention relates to a shut-off valve for an air bearing of an aircraft boost compressor.
A boost compressor supplies pressurized air to various systems of an aircraft. The boost compressor receives engine bleed air through an intake and compresses this air through a compressor rotor, which then supplies the compressed air to the system requiring pressurized air. The boost compressor is typically powered by a turbine that is driven by engine bleed air received by the other end of the boost compressor. The turbine rotor is attached to the same shaft as the compressor rotor. Engine bleed air passes over the turbine rotor causing the shaft and accordingly the compressor rotor to spin.
The shaft of the compressor rotor is cooled by an air bearing. Air is supplied to the air bearing through an air flow path that winds its way from the compressor inlet through various mechanical components to the air bearing. To avoid contaminating the air bearing, air received through the compressor air inlet is filtered by a J-tube air filter, which receives a portion of air received by the compressor air inlet. The J-tube filters out particles that may also flow with the air received by the compressor air inlet.
For certain applications, the boost compressor may be used infrequently and lay dormant for a fair amount of time. For example, the boost compressor may be used with an onboard inert gas generation system. This system provides inert gas to the fuel tanks of an aircraft, which serves to prevent fire in the fuel tanks. The system receives air from an air separation module and depletes the air of oxygen, leaving a nitrogen or inert gas enriched air to be fed to the fuel tanks.
To function properly, the air separation module requires air to be passed through at a certain air pressure. While this air pressure is normally supplied by bleed air from the engine of the aircraft, there are instances where the air pressure is insufficient for the air separation module to work properly. In such instances, such as a rapid aircraft descent, the boost compressor provides the onboard inert gas generation system with compressed air. Typically, the boost compressor does so infrequently.
As a consequence, the boost compressor is susceptible to problems caused by its dormancy. First, while dormant, contaminated air may flow through the J-tube of the boost compressor and into the air bearings, thereby leading to compressor malfunction. While the J-tube limits some of the contamination, it is insufficient to serve as an air filter at the very low flow rates that occur when the boost compressor is not operating.
In addition, particulates may accumulate in the ductwork leading into the compressor inlet during long periods of inactivity. When the boost compressor starts up, these particulate may suddenly overload the J-tube as an air filter. Consequently, these particulates may contaminate the air bearing.
A need therefore exists to address the problem of air bearing contamination that results from infrequent use of the boost compressor.